N = int(input())
C = list(input())

r = C.count("R")

cnt = 0
for i in range(r):
    if C[i] == "W":
        cnt += 1
        
print(cnt) N = int(input()) N int(input()) int input() input C = list(input()) C list(input()) list input() input r = C.count("R") r C.count("R") C.count C count "R" cnt = 0 cnt 0 for i in range(r):
    if C[i] == "W":
        cnt += 1
         i range(r) range r if C[i] == "W":
        cnt += 1
         C[i] == "W" C[i] C i "W" cnt += 1 cnt 1 print(cnt) print cnt r = C.count("R") C.count("R") r cnt = 0 0 cnt N = int(input()) int(input()) N cnt += 1 1 cnt C = list(input()) list(input()) C
N = int(input())
C = list(input())

r = C.count("R")

cnt = 0
for i in range(r):
    if C[i] == "W":
        cnt += 1
        
print(cnt)